--- changelog: category: Release version: 20260921.220548.000000000 date: '2026-09-21T22:05:48Z' seo: description: >- Finished Mon, Sep 21, 2026, 6:05 PM ET: all 3 core problems closed, 3 problems closed that day. Scheduled: Mon Sep 21, 2026 · Phase: Phase IV — Relational ·… title: Topic 16 — Graph DFS type: changelog --- Finished Mon, Sep 21, 2026, 6:05 PM ET: all 3 core problems closed, 3 problems closed that day. **Scheduled:** Mon Sep 21, 2026 · **Phase:** Phase IV — Relational · **Topic:** #18 · **Builds on:** Topic 11 + visited set ## Closed Sep 21 — the day the topic finished | Issue | Problem | Set | Difficulty | Closed (ET) | Solution | | --- | --- | --- | --- | --- | --- | | #130 | LC 200 · Number of Islands | core | medium | Sep 21 | [py](https://github.com/prdlk/leetcode/blob/20260921.220548.000000000/work/1/Medium/Array/200.number-of-islands.py) · [docs](https://lc.prd.lk/200) | | #131 | LC 133 · Clone Graph | core | medium | Sep 21 | [py](https://github.com/prdlk/leetcode/blob/20260921.220548.000000000/work/1/Medium/Hash%20Table/133.clone-graph.py) · [docs](https://lc.prd.lk/133) | | #132 | LC 417 · Pacific Atlantic Water Flow | core | medium | Sep 21 | [py](https://github.com/prdlk/leetcode/blob/20260921.220548.000000000/work/1/Medium/Array/417.pacific-atlantic-water-flow.py) · [docs](https://lc.prd.lk/417) | ## Open at release | Issue | Problem | Set | Difficulty | Closed (ET) | Solution | | --- | --- | --- | --- | --- | --- | | #133 | LC 695 · Max Area of Island | optional | medium | — | — | | #134 | LC 130 · Surrounded Regions | optional | medium | — | — | | #135 | LC 399 · Evaluate Division | optional | medium | — | — | | #136 | LC 261 · Graph Valid Tree | optional | medium | — | — | | #219 | LC 1254 · Number of Closed Islands | optional | medium | — | — | --- `20260921.220548.000000000` is [timever](https://gist.github.com/twolfson/de1b004dd22536b8e668) for the UTC instant the core set completed; it tags ae1d1ce, the last main commit before it.